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Chapter 11 - 1

Chapter 11: Applications and Processing of Metal Alloys

ISSUES TO ADDRESS... • How are metal alloys ____________ and what are their common applications ? • What are some of the common ____________ techniques for _________? • What heat treatment procedures are used to improve the mechanical properties of both __________________ alloys?

Chapter 11 - 2

Adapted from Fig. 9.24, Callister & Rethwisch 8e. (Fig. 9.24 adapted from Binary Alloy Phase Diagrams, 2nd ed., Vol. 1, T.B. Massalski (Ed.-in-Chief), ASM International, Materials Park, OH, 1990.)

Adapted from Fig. 11.1, Callister & Rethwisch 8e.

Classification of Metal Alloys Metal Alloys

Steels

Ferrous Nonferrous

Cast Irons <1.4wt%C 3-4.5 wt%C _______

_________ __________ ___________

Fe 3 C cementite

1600 1400 1200 1000 800 600 400

0 1 2 3 4 5 6 6.7

L γ

austenite γ +L

γ +Fe3C α

ferrite α +Fe3C

α + γ

L+Fe3C

δ

(Fe) Co , wt% C

Eutectic:

Eutectoid: 0.76

4.30

727ºC

1148ºC

T(ºC) microstructure: ferrite, graphite/cementite

Chapter 11 - 3 Based on data provided in Tables 11.1(b), 11.2(b), 11.3, and 11.4, Callister & Rethwisch 8e.

Steels Low Alloy High Alloy

low carbon <0.25 wt% C

Med carbon 0.25-0.6 wt% C

high carbon 0.6-1.4 wt% C

Uses auto struc. sheet

bridges towers press. vessels

crank shafts bolts hammers blades

pistons gears wear applic.

wear applic.

drills saws dies

high T applic. turbines furnaces

Very corros. resistant

Example 1010 4310 1040 43 40 1095 4190 304, 409 Additions none Cr,V

Ni, Mo none Cr, Ni Mo none Cr, V,

Mo, W Cr, Ni, Mo

plain HSLA plain heat treatable plain tool stainless Name

Hardenability 0 + + ++ ++ +++ varies TS - 0 + ++ + ++ varies EL + + 0 - - -- ++

increasing strength, cost, decreasing ductility

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Chapter 11 - 4

Refinement of Steel from Ore

Iron Ore ________

_____________

_______________________ →

C + O2 → CO2

CO2 + C → 2CO

CaCO3 → CaO+CO2 CaO + SiO2 + Al2O3 → slag

purification

reduction of iron ore to metal

heat generation

Molten iron

BLAST FURNACE

slag air

layers of ______ and __________

gas refractory vessel

Chapter 11 - 5

Ferrous Alloys Iron-based alloys

Nomenclature for steels (AISI/SAE) 10xx ____________________ 11xx Plain Carbon Steels (resulfurized for machinability) 15xx Mn (1.00 - 1.65%) 40xx Mo (0.20 ~ 0.30%) 43xx Ni (1.65 - 2.00%), Cr (0.40 - 0.90%), Mo (0.20 - 0.30%) 44xx Mo (0.5%)

where xx is wt% C x 100 example: 1060 steel – plain carbon steel with 0.60 wt% C

____________________ >11% Cr

• Steels • Cast Irons

Chapter 11 - 6

Cast Irons •  Ferrous alloys with > ____________

– more _________________________ •  Low melting – relatively easy to cast •  Generally brittle

•  Cementite decomposes to _____ + ________ Fe3C 3 Fe (α) + C (__________)

– generally a slow process

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Chapter 11 - 7

Fe-C True Equilibrium Diagram

Adapted from Fig. 11.2, Callister & Rethwisch 8e. [Fig. 11.2 adapted from Binary Alloy Phase Diagrams, 2nd ed., Vol. 1, T.B. Massalski (Ed.-in-Chief), ASM International, Materials Park, OH, 1990.]

1600

1400

1200

1000

800

600

400 0 1 2 3 4 90

L γ +L

α + Graphite

Liquid + Graphite

(Fe) C, wt% C

0.65

740ºC

T(ºC)

γ + Graphite

100

1153ºC γ Austenite 4.2 wt% C

α + γ

Graphite formation promoted by

•  __________

•  __________

Chapter 11 - 8

Types of Cast Iron Adapted from Fig. 11.3(a) & (b), Callister & Rethwisch 8e.

______ iron •  _________________ •  weak & brittle in tension •  stronger in compression •  excellent _________ dampening •  wear resistant

________ iron •  add Mg and/or Ce •  graphite as ________ not flakes •  matrix often pearlite – stronger

but less ductile

Chapter 11 - 9

Types of Cast Iron (cont.) Adapted from Fig. 11.3(c) & (d), Callister & Rethwisch 8e.

White iron •  < 1 wt% Si •  pearlite + ________ •  very hard and _______

__________ iron •  heat treat white iron at 800-900ºC •  graphite in __________ •  reasonably strong and ductile

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Chapter 11 - 10

Types of Cast Iron (cont.)

Adapted from Fig. 11.3(e), Callister & Rethwisch 8e.

Compacted _________ iron •  relatively high _________________ •  good resistance to thermal shock •  lower oxidation at elevated

temperatures

Chapter 11 - 11

Production of Cast Irons

Adapted from Fig.11.5, Callister & Rethwisch 8e.

Chapter 11 - 12

Limitations of Ferrous Alloys

1)  Relatively high densities 2)  Relatively low electrical conductivities 3)  Generally poor corrosion resistance

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Chapter 11 - 13 Based on discussion and data provided in Section 11.3, Callister & Rethwisch 3e.

Nonferrous Alloys

NonFerrous Alloys

• Al Alloys -low ρ: 2.7 g/cm3 -Cu, Mg, Si, Mn, Zn additions -solid sol. or precip. strengthened (struct.

aircraft parts & packaging)

• Mg Alloys -very low ρ : 1.7g/cm3 -ignites easily - aircraft, missiles

• Refractory metals -high melting T’s -Nb, Mo, W, Ta • Noble metals

-Ag, Au, Pt - oxid./corr. resistant

• Ti Alloys -relatively low ρ: 4.5 g/cm3

vs 7.9 for steel -reactive at high T’s - space applic.

• Cu Alloys Brass: Zn is subst. impurity (costume jewelry, coins, corrosion resistant) Bronze : Sn, Al, Si, Ni are subst. impurities (bushings, landing gear) Cu-Be : precip. hardened for strength

Chapter 11 -

•  How do we fabricate metals? –  ___________ - hammer (forged) –  Cast molten metal into mold

•  ___________________ –  Rough stock formed to final shape

Hot working vs. Cold working

14

Metal Fabrication

• Deformation ____________ high enough for ________________ • Large ______________

• Deformation below ________________ temperature • Strain hardening occurs • Small ______________

Chapter 11 - 15

FORMING

roll A o

A d roll

• Rolling (________________) (I-beams, rails, sheet & plate)

A o A d

force die

blank

force

• Forging (__________________) (wrenches, crankshafts)

often at elev. T

Adapted from Fig. 11.8, Callister & Rethwisch 8e.

Metal Fabrication Methods (i)

ram billet container

container force die holder

die

A o

A d extrusion

• __________ (rods, tubing)

ductile metals, e.g. Cu, Al (hot)

tensile force A o

A d die

die

• Drawing (rods, wire, tubing)

die must be well lubricated & clean

CASTING MISCELLANEOUS

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Chapter 11 - 16

FORMING CASTING

Metal Fabrication Methods (ii)

•  Casting- mold is filled with molten metal –  __________________________, perhaps alloying

elements added, then _______ in a mold –  ____________________________ –  gives good production of shapes –  weaker products, internal defects –  ____________________________

MISCELLANEOUS

Chapter 11 - 17

• ________ Casting (large parts, e.g., auto engine blocks)

Metal Fabrication Methods (iii)

•  What material will withstand T >1600ºC and is ____________ and easy to mold?

•  Answer: ________!!!

•  To create mold, pack _____ around form (pattern) of desired shape

Sand Sand molten metal

FORMING CASTING MISCELLANEOUS

Chapter 11 - 18

•  Stage I — _____ formed by pouring ____________ around wax pattern. Plaster allowed to harden.

• Stage II — Wax is melted and then poured from mold—hollow mold cavity remains.

• Stage III — ___________________ into mold and allowed to solidify.

Metal Fabrication Methods (iv)

FORMING CASTING MISCELLANEOUS • _____________________ (low volume, complex shapes e.g., jewelry, turbine blades)

wax I

II

III

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Chapter 11 - 19

Metal Fabrication Methods (v)

• Continuous Casting -- _________ shapes (e.g., rectangular slabs, cylinders)

molten solidified

FORMING CASTING MISCELLANEOUS

• Die Casting -- high ____________ -- for alloys having ____ melting temperatures

Chapter 11 - 20

MISCELLANEOUS CASTING

Metal Fabrication Methods (vi)

pressure

heat

point contact at low T

densification by diffusion at higher T

area contact

densify

FORMING • _______________ (metals w/low ductilities)

• _____________ (when fabrication of one large part is impractical)

• Heat-affected _______: (region in which the microstructure has been changed).

Adapted from Fig. 11.9, Callister 7e. (Fig. 11.9 from Iron Castings Handbook, C.F. Walton and T.J. Opar (Ed.), 1981.)

piece 1 piece 2

fused base metal filler metal (melted)

base metal (melted)

unaffected unaffected heat-affected zone

Chapter 11 - 21

Annealing: Heat to Tanneal, then cool slowly.

Based on discussion in Section 11.7, Callister & Rethwisch 8e.

Thermal Processing of Metals

Types of Annealing

• _______________: Negate effects of

cold working by (recovery/ recrystallization)

• Stress Relief: Reduce stresses resulting from:

- plastic deformation - ___________ cooling - phase transform.

• _________ (steels): Deform steel with large grains. Then heat treat to allow _______________ and formation of smaller grains.

• Full Anneal (steels): Make soft steels for good forming. Heat to get γ , then furnace-cool to obtain coarse pearlite.

• __________ (steels): Make very soft steels for

good machining. Heat just below Teutectoid & hold for 15-25 h.

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Chapter 11 - 22

a)  _____________ b)  _____________

Heat Treatment Temperature-Time Paths

c)

c)  Tempering (Tempered Martensite)

P

B

0%

100% 50%

A

A

a) b)

Fig. 10.25, Callister & Rethwisch 8e.

Chapter 11 - 23

Hardenability -- Steels • __________ – measure of the ability to form martensite • Jominy end quench test used to measure ____________.

• Plot __________ versus distance from the quenched end.

Adapted from Fig. 11.11, Callister & Rethwisch 8e. (Fig. 11.11 adapted from A.G. Guy, Essentials of Materials Science, McGraw-Hill Book Company, New York, 1978.)

Adapted from Fig. 11.12, Callister & Rethwisch 8e.

24ºC water

specimen (heated to γ phase field)

flat ground

Rockwell C hardness tests

Har

dnes

s, H

RC

Distance from quenched end

Chapter 11 - 24

• The cooling rate _________ with distance from quenched end.

Adapted from Fig. 11.13, Callister & Rethwisch 8e. (Fig. 11.13 adapted from H. Boyer (Ed.) Atlas of Isothermal Transformation and Cooling Transformation Diagrams, American Society for Metals, 1977, p. 376.)

Reason Why Hardness Changes with Distance

distance from quenched end (in) Har

dnes

s, H

RC

20 40 60

0 1 2 3

600

400

200 A → M

A → P

0.1 1 10 100 1000

T(ºC)

M(start)

Time (s)

0

0% 100%

M(finish) Martensite Martensite + Pearlite

Fine Pearlite

Pearlite

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Chapter 11 - 25

Hardenability vs Alloy Composition • _____________ curves for five alloys each with, C = ______________

• "Alloy Steels" (4140, 4340, 5140, 8640) -- contain Ni, Cr, Mo (0.2 to 2 wt%) -- these ___________ shift the "nose" to longer times (from A to B) -- martensite is easier to form

Adapted from Fig. 11.14, Callister & Rethwisch 8e. (Fig. 11.14 adapted from figure furnished courtesy Republic Steel Corporation.)

Cooling rate (ºC/s)

Har

dnes

s, H

RC

20

40

60

10 0 20 30 40 50 Distance from quenched end (mm)

2 10 100 3

4140 8640 5140

1040

50 80

100 %M 4340

T(ºC)

10 -1 10 10 3 10 5 0

200

400

600

800

Time (s)

M(start) M(90%)

B A TE

Chapter 11 - 26

• Effect of quenching medium: Medium

air oil

water

• Effect of specimen geometry: When surface area-to-volume ratio increases: -- cooling rate throughout interior increases -- hardness throughout interior increases

Position center surface

Cooling rate low high

Hardness low high

Influences of Quenching Medium & Specimen Geometry

Severity of Quench ________ ________ ________

Hardness ________ ________ ________

Chapter 11 - 27

0 10 20 30 40 50 wt% Cu

L α+L α

α+θ θ

θ+L

300 400 500

600 700

(Al)

T(ºC)

composition range available for precipitation hardening

CuAl2

A

Adapted from Fig. 11.24, Callister & Rethwisch 8e. (Fig. 11.24 adapted from J.L. Murray, International Metals Review 30, p.5, 1985.)

Precipitation Hardening

Adapted from Fig. 11.22, Callister & Rethwisch 8e.

•  Other alloys that precipitation harden: • Cu-Be • Cu-Sn • Mg-Al

Temp.

Time

Pt A (sol’n heat treat)

B

Pt B

C

Pt C (precipitate θ)

• Particles impede ___________ motion. • Ex: Al-Cu system • Procedure:

--Pt B: _______ to room temp. (retain α solid solution) --Pt C: ________ to nucleate small θ __________ within α phase.

--Pt A: _______________ (get α solid solution)

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Chapter 11 - 28

• 2014 Al Alloy:

Adapted from Fig. 11.27, Callister & Rethwisch 8e. (Fig. 11.27 adapted from Metals Handbook: Properties and Selection: Nonferrous Alloys and Pure Metals, Vol. 2, 9th ed., H. Baker (Managing Ed.), American Society for Metals, 1979. p. 41.)

Influence of Precipitation Heat Treatment on TS, %EL

precipitation heat treat time

tens

ile s

treng

th (M

Pa)

200

300

400

100 1min 1h 1day 1mo 1yr 204ºC

non-

equi

l.

solid

sol

utio

n m

any

smal

l pr

ecip

itate

s

“age

d”

fe

wer l

arge

pr

ecip

itate

s

“ove

rage

d”

149ºC

• ________ on TS curves. • __________ T accelerates process.

• ________ on %EL curves.

%E

L (2

in s

ampl

e)

10

20

30

0 1min 1h 1day 1mo 1yr

204°C 149 °C

precipitation heat treat time

Chapter 11 - 29

• Ferrous alloys: steels and cast irons • Non-ferrous alloys: -- Cu, Al, Ti, and Mg alloys; refractory alloys; and noble metals. • Metal fabrication techniques: -- forming, casting, miscellaneous. • Hardenability of metals -- measure of ability of a steel to be heat treated. -- increases with alloy content. • Precipitation hardening --hardening, strengthening due to formation of precipitate particles. --Al, Mg alloys precipitation hardenable.

Summary